Seeing the reference to Grammarly on the Writing Resources post I decided to explore it further. I plugged in the first chapter of the book I'm working on - a personal testimony - and checked to see what they would come up with. I wasn't really surprised that they found a couple of grammar and punctuation errors, nor the spelling error, but I was stunned when they found plagiarism. That simply isn't possible. So is this a gimmick they do to encourage people to subscribe to their program, or has someone managed to somehow get a copy of my draft and put it out as their own? If I subscribe will I find out where they think I took it from? do they claim plagiarism for the entire work, a few paragraphs, or just a sentence?
Anyone have any experience with this?

I don't know--I've never seen that particular notification come up. A few things occur to me: was it a place where you were quoting scripture or some other published work? (That's not plagiarism, it's legitimate). Or was it a passage using a familiar phrase like (just tossing something out there) "out of the frying pan, into the fire"? Or were you telling a paraphrased or re-written version of a familiar scenario? (If that's the case, maybe having a certain percent of key words within close proximity sets off their alerts).

I doubt that it's a trick or a marketing gimmick--it's more likely that it's one of the inherent problems with any non-human grammar checker--they just make errors. (That's why I encourage people to carefully consider their suggestions). In my own use of it, I've found it far superior to the grammar checker in MS Word, but still with errors and a bit of a lack of sophistication. I use it to catch typos, mainly--but it has no idea what to do with "gimmicks" like intentional fragments or other tricks of voice.

Unless you'd posted drafts of your testimony somewhere, I don't see how anyone else could have got them. Oh wait a minute--if any of that chapter was posted here, on FaithWriters, (or anywhere else online), that could be what they picked up.

I have the paid version of Grammarly. If you'd like, you could email me your chapter and I could see what additional information I can get on their plagiarism alert. PM me if you're interested and I'll send you my email address.